1. Field of the Invention
The present invention relates to a high-frequency dielectric ceramic composition and to a dielectric resonator, a dielectric filter, a dielectric duplexer and a communication apparatus using the same.
2. Description of the Related Art
Dielectric ceramic components are widely used as dielectric resonators, dielectric filters and circuit board materials which are mounted in electronic devices, such as portable phones, personal radio equipment and satellite broadcasting receivers, used in high-frequency bands including microwave bands and millimeter-wave bands.
Dielectric characteristics required for these high-frequency dielectric ceramic components includes (1) a high specific dielectric constant (∈r) for achieving a decrease in size of the component due to a reduction in electromagnetic wavelength in a dielectric material to 1/(∈r)xc2xd, (2) a low dielectric loss, that is, a high Q value, and (3) high stability of resonant frequencies to temperature, that is, a temperature coefficient (xcfx84f) of the resonant frequency near zero (ppm/xc2x0C.).
Examples of disclosed dielectric ceramic compositions include a Ba(Zn,Ta)O3-based composition (Japanese Examined Patent Application Publication No. 58-25068), a Ba(Sn,Mg,Ta)O3-based composition (Japanese Examined Patent Application Publication No. 3-34164), a (Zr,Sn)TiO4-based composition (Japanese Examined Patent Application Publication No. 4-59267) and Ba2Ti9O20 (Japanese Unexamined Patent Application Publication No. 61-10806).
Among these, Ba(Zn,Ta)O3-based and Ba(Sn,Mg,Ta)O3-based compositions have significantly high Q values in a range of 150,000 to 300,000 at 1 GHz, but exhibit relatively small specific dielectric constants (∈r) in a range of 24 to 30.
In contrast, the (Zr,Sn)TiO4-based composition and Ba2Ti9O20 exhibit relatively large specific dielectric constants (∈r) in a range of 37 to 40 and large Q values in a range of 50,000 to 60,000 at 1 GHz. These materials, however, do not exhibit specific dielectric constants exceeding 40.
In recent years, more compact and low-loss electronic components have been required. However, no dielectric material having a higher specific dielectric constant (∈r) and a higher Q value applicable to these electronic components has been developed.
It is an object of the present invention to provide a high-frequency dielectric ceramic composition having a specific dielectric constant (∈r) as high as 40 to 60, a Q value as high as 30,000 or more at 1 GHz, and a small temperature coefficient (xcfx84f) of resonant frequency within 0xc2x130 (ppm/xc2x0C.).
It is another object of the present invention to provide a dielectric resonator, a dielectric filter, a dielectric duplexer and a communication apparatus using the high-frequency dielectric ceramic composition.
A high-frequency dielectric ceramic composition of the present invention comprises a perovskite crystal phase and comprises a rare earth element Ln, aluminum, calcium, zinc, M, and titanium wherein M is at least one of niobium and tantalum, wherein the composition is represented by the formula:
(1xe2x88x92y)xCaTiaO1+2axe2x88x92(1xe2x88x92y)(1xe2x88x92x)Ca(Zn⅓M⅔)bO1+2bxe2x88x92yLnAlcO(3+3c)/2
wherein x and y represent molar ratios, and x, y, (1xe2x88x92y)x, a, b, and c satisfy the relationships: 0.56xe2x89xa6xxe2x89xa60.8, 0.08xe2x89xa6yxe2x89xa60.18, (1xe2x88x92y)xxe2x89xa60.65, 0.985xe2x89xa6axe2x89xa61.05, 0.9xe2x89xa6bxe2x89xa61.02, and 0.9xe2x89xa6cxe2x89xa61.05.
The high-frequency dielectric ceramic composition may further comprises magnesium, and the composition is represented by the formula:
(1xe2x88x92y)xCaTiaO1+2axe2x88x92(1xe2x88x92y)(1xe2x88x92x)Ca {(Znxe2x88x92zMg)⅓M⅔}bO1+2bxe2x88x92yLnAlcO(3+3c)/2
wherein x and y represent molar ratios, and x, y, z, (1xe2x88x92y)x, a, b, and c satisfy the relationships: 0.56xe2x89xa6xxe2x89xa60.8, 0.08xe2x89xa6yxe2x89xa60.18, 0 less than z less than 1, (1xe2x88x92y)xxe2x89xa60.65, 0.985xe2x89xa6axe2x89xa61.05,0.9xe2x89xa6bxe2x89xa61.02, and 0.9xe2x89xa6cxe2x89xa61.05.
Preferably, xcex1xe2x89xa60.6.
Preferably, the rare earth element Ln is at least one selected from neodymium, yttrium, lanthanum, samarium and praseodymium. More preferably, the rare earth element Ln is at least one selected from neodymium and lanthanum.
A dielectric resonator of the present invention comprises a dielectric ceramic component and input/output terminals, the dielectric resonator operating by electromagnetic coupling of the dielectric ceramic component with the input/output terminals, wherein the dielectric ceramic component comprises the above high-frequency dielectric ceramic composition.
A dielectric filter of the present invention comprises the above dielectric resonator and external coupling means.
A dielectric duplexer of the present invention comprises at least two dielectric filters, input/output connecting means, each connected to each of the dielectric filters, and antenna connecting means commonly connected to the dielectric filters, wherein at least one of the dielectric filters is the above-mentioned dielectric filter.
A communication apparatus of the present invention comprises the above dielectric duplexer, a transmitting circuit connected to at least one input/output connecting means of the dielectric duplexer, a receiving circuit connected to at least another input/output connecting means which is different from said at least one input/output connecting means, and an antenna connected to the antenna connecting means of the dielectric duplexer.